The instant invention relates to a well tool and more particularly to such a tool which is designed to be set into a well casing on a wire line.
Various kinds of well tools are constructed to be lowered into a casing and anchored to the casing at a selected level. Such anchoring is typically achieved by expandable slips which grip the casing to prevent movement of the tool when expanded. In most such tools, a slidable portion on the body of the tool slides from a first position to a second position in order to effect slip expansion. On tools of the retrievable type, the slidable portion includes drag blocks which frictionally engage the interior casing surface. When the tool is lowered, a locking mechanism maintains the drag blocks in a position which prevents slip expansion. The tool is lowered on a drill string which is then manipulated to effect movement of the tool body relative to the drag blocks in order to release the locking mechanism to permit slip expansion.
Some tools are intended to be anchored to the casing only once and thereafter retrieved. Generally, such tools are suspended from a conventional wire line setting assembly which in turn is suspended from a wire line and lowered into a casing. The wire line setting assembly includes a power source, typically a hydraulic cylinder, which is attached to the slidable portion of the tool. When the tool is positioned at a desired depth, a signal from the surface actuates the piston which moves the slidable portion of the tool into the position in which the slips expand thus anchoring the tool. The same piston movement which sets the tool shears a bolt connecting the setting assembly to the tool and, after setting, the setting assembly and wire line are raised to the surface. A conventional drill string is used to retrieve the tool to the surface. Due to the construction of such tools, the tool must be retrieved to the surface prior to resetting the tool in the casing. Such retrieval is necessary to repair the setting mechanism which may require, e.g., new shear bolts.
It can be readily seen that setting such tools on a wire line provides a great saving in time and labor expense over setting of tools on drill strings. When a tool is set on a drill string, the pipe must be added to the string one section at a time as the tool is lowered into the casing. This is time consuming as well as labor extensive in that a drilling rig operator must start and stop the drill power source to permit several men to add tubing to the drill string one section at a time. When a wire line is used to set a tool, the tool is suspended from the line and the line is typically unwound from a reel, thus permitting quick lowering of the tool to a selected depth. A main drawback of prior tools which are set on wire lines is that they must be retrieved to the surface prior to resetting the tool at a different depth.
It is an object of the present invention to provide a tool and a method for using the same which permits an initial setting of the tool in the well casing on a wire line and thereafter permits unsetting and retrieval or resetting of the tool in the casing with the use of a drill string.
It is another object of the invention to provide such a tool which can be used with a conventional wire line setting assembly and with a conventional overshot suspended from a drill string.
It is a more specific object of the invention to provide such a tool which, although retrievable and resettable, may be firmly locked in a casing-engaging condition when set.
The instant invention includes a tool having a body with anchor slips mounted thereabout. The slips are attached to drag blocks which move from a first position to a second position in order to expand the slips for engagement to the casing. A slidable abutment is provided adjacent the drag blocks for moving them to their second position. A lug on the drag blocks is received within a channel formed in the tool body. Initially, shear bolts connect the drag blocks to the tool body to maintain the blocks in their first position. The tool is lowered into the casing on a conventional wire line setting assembly which includes means for selectively moving the slidable abutment so as to shear the shear bolts while moving the drag blocks from their first to their second position. A ratchet locking means disposed between the drag blocks and the tool body is provided to maintain the slips in a casing-engaging condition.
When it is desired to retrieve or to reset the tool at a different depth in the casing, a drill string is lowered having a conventional overshot suspended therefrom. The drill string is connected to the tool with the overshot. Manipulation of the drill string effects rotational and longitudinal movement of the tool body relative to the drag blocks. Such movement unlocks the ratchet mechanism and permits movement of the drag blocks to their first position. Thereafter, the tool may be retrieved or reset in the casing, such resetting being effected with drill string manipulation to achieve movement of the drag blocks relative to the tool body.
These and other objects and advantages of the invention will become more fully apparent when the following detailed description is read in view of the accompanying drawings.